1. Field of the Invention
The present invention relates to a system for automatically removing view-obstructing materials such as ice, dirt or inside condensation from the windows of a vehicle, and more particularly to a system for heating the windshield cleaning fluid in the vehicle before it is sprayed on the windshield.
2. Description of the Prior Art
The need to automatically remove view-obstructing materials such as ice, snow, sleet, condensation or dirt from the windows of a vehicle is a well-known problem. For example, FIG. 1 illustrates a system for spraying a stream of cleaning fluid on a windshield that is available in most of the passenger vehicles sold in the United States today. A problem with this type of system is that it is not very effective at removing frozen precipitation such as ice or snow, or in removing other view-obstructing materials, such as impacted insects, from the windshield.
Products are commercially available that attempt to improve the performance of the system shown in FIG. 1 by providing a means for heating the cleaning fluid before it is sprayed on the windshield. One type of product includes a heating element that is immersed in the cleaning fluid reservoir 12 (shown in FIG. 1) in order to heat all of the fluid in the reservoir. A problem with this technique is that heating the entire reservoir is a very slow process. Additionally, the temperature to which the cleaning fluid can be heated is limited by the material from which the reservoir is constructed. Another product, used to prevent the windshield cleaning fluid from freezing, includes a second tube that is positioned in close proximity to the tube 16 of FIG. 1. Engine coolant fluid is directed through the second tube to heat the cleaning fluid contained in the tube 16. However, this is not a very effective process because the efficiency of heat transfer between the two tubes is not great and because it is impractical to have the two tubes run in parallel over a long distance.
Another approach is to direct the windshield cleaning fluid into a separate vessel in which the heating of the fluid takes place. For example, O. Rocchitelli, in U.S. Pat. No. 4,508,957 (issued Apr. 2, 1985), describes a cartridge-type device that uses thermistors to heat the windshield cleaning fluid flowing through the cartridge device.
Similarly, H. Schlick, in U.S. Pat. No. 4,212,425 (issued Jul. 15, 1980) and U.S. Pat. No. 4,088,269 (issued May 9, 1978), describes a spray nozzle that utilizes a PTC thermistor heating element to heat windshield cleaning fluid before it is sprayed on a windshield. None of these devices utilize optimized designs or disclose control circuitry for controlling the functioning of the heating devices.
Additional patents that are related to the field of windshield cleaning fluid heating technology include: U.S. Pat. No. 4,832,262 (H. Robertson et al., May 23, 1989) which discloses a heat exchanger that utilizes the exhaust system of an internal combustion engine for heating the windshield cleaning fluid; U.S. Pat. No. 4,798,230 (S. Hopperdietzel, Jan. 17, 1989) which discloses a plastic hose having embedded conductors for heating fluid contained in the hose; U.S. Pat. No. 4,575,003 (R. Linker, et al., Mar. 11, 1986) which discloses a system that utilizes the engine coolant system to heat the windshield cleaning fluid; and U.S. Pat. No. 3,888,412 (H. Lindo, Jun. 10, 1975) which also discloses a system that utilizes the engine coolant system to heat windshield cleaning fluid.